Tool holder

ABSTRACT

A tool holder is equipped with a tip run-out correction mechanism for correcting run-out of the tip of the tool. The tip run-out correction mechanism includes an annular stepped portion formed on a cylindrical support portion of a holder body; a ring member rotatably fitted onto the annular stepped portion; an eccentric cam disposed within the ring member, the eccentric cam extending radially through the ring member and being rotatable about a radially extending axis; and a pin disposed within the ring member to be movable along a direction parallel to the center axis of a flange portion of the holder body. One end of the pin is in contact with the eccentric cam, and the other end of the pin is in contact with a rear end face of a clamp sleeve which clamps a tool inserted into a chuck sleeve of the holder body. The eccentric cam is rotated so as to adjust press force that the pin applies to the rear end face of the clamp sleeve, to thereby elastically deform a base end portion of the chuck sleeve in a radial direction in such a manner that tip run-out of the tool approaches zero.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a divisional application of pending priorU.S. Divisional Application No. 11/264,426 filed on Oct. 31, 2005 nowU.S. Pat. No. 7,165,923, which is a divisional of U.S. Ser. No.10/387,086, filed on Mar. 12, 2003 (and is now granted U.S. Patent No.7,037,053 B2 issued May 2, 2006), which claims the priority to JapanesePatent Application Numbers 2002-73809, filed on Mar. 18, 2002 and2002-114147, filed on Apr. 17, 2002, the contents of which areincorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a tool holder which is used to attach acutting tool, such as a burnishing reamer or a drill, to a main spindleof a machine tool, and which can correct run-out of the tip of thecutting tool.

2. Description of the Related Art

In machining performed by a machine tool, a cutting tool must beattached to a main spindle of the machine tool with high accuracy inorder to enable accurate machining.

In general, in the case where a cutting tool is chucked by use of a toolholder, run-out of the cutting tool as measured at a point located awayfrom the chucked portion of the cutting tool toward the tip thereof by apredetermined distance is used as an index that represents run-outaccuracy. Even a precision tool holder has a run-out accuracy of 3 to 5μm. In other words, even when a precision chuck is used for a toolholder of a burnishing reamer, drill, or the like, difficulty isencountered in reducing run-out of the tip of the tool to zero.Therefore, a tool holder capable of correcting run-out of the tip of atool has been proposed and put to practical use.

Conventional tool holders equipped with a tip run-out correctingmechanism will be described with reference to FIGS. 1 and 2.

FIG. 1 is a partially sectioned side view of a conventional tool holderequipped with a tip run-out correcting mechanism.

As shown in FIG. 1, a tool holder 1 includes a taper shank portion 2 tobe attached to a main spindle of an unillustrated machine tool; a flange3, which is formed at a larger-diameter-side end of the shank portion 2and used for gripping the tool holder 1; and an arbor 4, which is formedintegrally with the flange 3 in such a manner that the arbor 4 extendsfrom an end of the flange 3 opposite the shank portion 2, and its axisis aligned with that of the flange 3. A cutting tool 6 such as a drillis attached to a tip portion of the arbor 4 by means of a collet chuck5.

A shoulder portion 4 a having a diameter greater than that of the arbor4 is formed at a boundary between the arbor 4 and the flange 3. A rotaryring 7, which constitutes a tip run-out correcting mechanism, isrotatably fitted onto the shoulder portion 4 a. A fixation bolt 8radially penetrates the rotary ring 7 at an axial position facing theshoulder portion 4 a and is in screw-engagement with the rotary ring 7.Thus, the rotary ring 7 can be fixed to the shoulder portion 4 a bymeans of the fixation bolt 8. Further, four tip run-out correctingscrews 9 radially penetrate the rotary ring 7 at an axial positionfacing a root portion of the arbor 4 and are in screw-engagement withthe rotary ring 7.

When such a tool holder 1 is used, tip run-out of the cutting tool 6 iscorrected as follows. An operator attaches to a main spindle of amachine tool the shank portion 2 of the tool holder 1, which carries thecutting tool 6. Subsequently, the operator brings a test indicator 10into contact with a circumferential surface of a tip portion of thecutting tool 6. The operator measures the difference between the maximumand minimum readings of the test indicator 10 during rotation of themain spindle, as tip run-out of the cutting tool 6. Further, from themeasured value, the operator determines an angular position at which thetip run-out of the cutting tool 6 becomes greatest. Subsequently, afterrotation of the main spindle is stopped, the operator rotates the rotaryring 7 in such a manner that one of the correction screws 9 faces acircumferential surface section of the root portion of the arbor 4, thesurface section corresponding to the angular position at which the tiprun-out of the cutting tool 6 becomes greatest. The operator then fixesthe rotary ring 7 by means of the fixation bolt 8. Subsequently, whileviewing the test indicator 10, the operator tightens the correctionscrew 9 that faces the circumferential surface section of the rootportion of the arbor 4 corresponding to the angular position at whichthe tip run-out becomes greatest, in order to elastically deform thearbor 4 in the screwing direction of the correction screw 9, to therebycorrect the eccentricity of the tip of the cutting tool 6 in such amanner that the tip run-out of the cutting tool 6 approaches zero to apossible extent. Thus, the tip run-out of the cutting tool 6 can becorrected.

FIG. 2 is a partially sectioned side view of another conventional toolholder equipped with a tip run-out correcting mechanism.

As shown in FIG. 2, a tool holder 12 includes a taper shank 13 to beattached to a main spindle of an unillustrated machine tool; a flange14, which is formed at a larger-diameter-side end of the shank 13 andused for gripping the tool holder 12; and an arbor 15, which is formedintegrally with the flange 14 in such a manner that the arbor 15 extendsfrom an end of the flange 14 opposite the shank portion 13, and its axisis aligned with that of the flange 14. A cutting tool 17 such as a drillis attached to a tip portion of the arbor 15 by means of a collet chuck16.

In FIG. 2, reference numeral 18 denotes a run-out corrector forcorrecting tip run-out of the cutting tool 17 held on the tool holder 12via the collet chuck 16. The run-out corrector 18 includes a ring member181 and a push screw 182. The ring member 181 is removably attached to atip portion of the arbor 15 and the periphery of a lock nut 161 of thecollet chuck 16. The push screw 182 radially penetrates the ring member181 and is in screw-engagement with the ring member 181.

When such a tool holder 12 is used, tip run-out of the cutting tool 17is corrected as follows. An operator attaches to a main spindle of amachine tool the shank portion 13 of the tool holder 12, which carriesthe cutting tool 17. Subsequently, the operator brings a test indicator19 into contact with a circumferential surface of a tip portion of thecutting tool 17. The operator measures the difference between themaximum and minimum readings of the test indicator 19 during rotation ofthe main spindle, as tip run-out of the cutting tool 17. Further, frommeasured value, the operator determines an angular position at which thetip run-out of the cutting tool 17 becomes greatest. Subsequently, afterrotation of the main spindle is stopped, the operator rotates the ringmember 181 in such a manner that the push screw 182 faces a peripheralportion of the lock nut 161, the portion corresponding to the angularposition at which the tip run-out of the cutting tool 17 becomesgreatest. Subsequently, while viewing the test indicator 19, theoperator tightens the push screw 182 in order to apply pressure to thatperipheral portion in the direction indicated by an arrow, to therebycorrect the eccentricity of the tip of the cutting tool 17 in such amanner that the tip run-out of the cutting tool 17 approaches zero to apossible extent. Thus, the tip run-out of the cutting tool 17 can becorrected. After completion of run-out correction, the operator removesthe run-out corrector 18 from the tool holder 12.

However, in the case of the tool holder 1 shown in FIG. 1, when theeccentricity of the tip of a tool is to be corrected, an operator mustelastically deform the arbor 4 in a radial direction by radially pushingthe root portion of the arbor 4 by use of the corresponding correctionscrew 9 of the tip run-out correction mechanism. Therefore, correctionof tip run-out requires a large force. Therefore, such a conventionaltip run-out correction mechanism can be applied only to tool holders fortools of small diameters.

Further, in the case of the tool holder 12 shown in FIG. 2, since therun-out corrector 18 is removed from the tool holder 12, after beingcorrected the tip of a-tool may return to the original eccentric ordeviated position; i.e., the corrected position of the tip of the toolcannot be maintained stably.

SUMMARY OF THE INVENTION

In view of the foregoing, an object of the present invention is toprovide a tool holder equipped with a tip run-out correction functionwhich enables an operator to easily correct tip run-out of a cuttingtool with small force, can maintain high run-out accuracy attainedthrough correction, and can be applied to holders used for cutting toolsof large diameter.

In order to achieve the above-described object, the present inventionprovides a tool holder which comprises a holder body having a shankportion to be attached to a main spindle of a machine tool, a flangeportion-formed at an end of the shank portion and having a center axisaligned with a center axis of the shank portion, a support portionextending from the flange portion in a direction opposite the shankportion and having a center axis aligned with the center axis of theflange portion, and a chuck sleeve extending from a tip end of thesupport portion and having a center axis aligned with the center axis ofthe support portion, the chuck sleeve being elastically deformable andadapted to receive a shank portion of a tool; a clamp sleeve rotatablyfitted onto the chuck sleeve, the clamp sleeve being rotated relative tothe chuck sleeve to reduce a diameter of the chuck sleeve in order tohold the shank portion of the tool inserted into the chuck sleeve; and atip run-out correction mechanism for correcting run-out of the tip ofthe tool.

The tip run-out correction mechanism includes an annular stepped portionconcentrically formed on an outer circumference of the support portion;a ring member rotatably fitted onto the annular stepped portion; aneccentric cam disposed within the ring member, the eccentric camextending radially through the ring member and being rotatable about aradially extending axis; and a pin disposed within the ring member to bemovable along a direction parallel to the center axis of the flangeportion, one end of the pin being in contact with the eccentric cam andthe other end of the pin being in contact with a rear end face of theclamp sleeve or an end face of the annular stepped portion.

The eccentric cam is rotated so as to adjust press force that the pinapplies to the rear end face of the clamp sleeve or the end face of theannular stepped portion, to thereby elastically deform a base endportion of the chuck sleeve adjacent to the flange portion in a radialdirection in such a manner that tip run-out of the tool approaches zero.

Preferably, an annular groove is formed in a font end face of thesupport portion, from which the chuck sleeve extends axially, theannular groove promoting radial elastic deformation of the chuck sleeveand radial bending deformation of the chuck sleeve about the baseportion serving as a bending point.

Preferably, the ring member includes a balance member for preventingunbalanced rotation of the ring member, which would otherwise resultfrom provision of the eccentric cam.

Preferably, the ring member includes a lock screw for fixing the ringmember to the annular stepped portion.

Alternatively, the tip run-out correction mechanism includes an annularstepped portion concentrically formed on an outer circumference of thesupport portion; a ring member rotatably fitted onto the annular steppedportion; an operation member disposed within the ring member, theoperation member radially extending through the ring member and beingrotatable about a radially extending axis; and a ball element disposedwithin the ring member to be located between the operation member and arear end face of the clamp sleeve or an end face of the annular steppedportion, the ball element being movable along a direction parallel tothe center axis of the flange portion.

The operation member is rotated so as to adjust press force that theball element applies to the rear end face of the clamp sleeve or the endface of the annular stepped portion, to thereby elastically deform abase end portion of the chuck sleeve adjacent to the flange portion in aradial direction in such a manner that tip run-out of the toolapproaches zero.

Preferably, the operation member assumes a cylindrical shape; an arcuatecam groove is formed on an outer circumferential surface of theoperation member so as to be eccentric with respect to the axis of theoperation member; the ball element is received in the cam groove; andthe press force that the ball element applies to the rear end face ofthe clamp sleeve or the end face of the annular stepped portion isadjusted by means of the cam groove.

Preferably, an annular groove is formed in a font end face of thesupport portion, from which the chuck sleeve extends axially, theannular groove promoting radial elastic deformation of the chuck sleeveand radial bending deformation of the chuck sleeve about the baseportion serving as a bending point.

Preferably, the ring member includes a balance member for preventingunbalanced rotation of the ring member, which would otherwise resultfrom provision of the ball element.

Preferably, the ring member includes a lock screw for fixing the ringmember to the annular stepped portion.

The present invention further provides a tool holder which comprises aholder body having a shank portion to be attached to a main spindle of amachine tool, a flange portion formed at an end of the shank portion andhaving a center axis aligned with a center axis of the shank portion,and an arbor extending from the flange portion in a direction oppositethe shank portion and having a center axis aligned with the center axisof the flange portion; a chuck for holding a tool at a tip end of thearbor; and a tip run-out correction mechanism for correcting run-out ofthe tip of the tool.

The tip run-out correction mechanism includes a ring member rotatablyfitted onto a base portion of the arbor adjacent to the flange portion;a stopper member provided on the arbor so as to hold the ring member atthe base portion of the arbor; an eccentric cam disposed within the ringmember, the eccentric cam extending radially through the ring member andbeing rotatable about a radially extending axis; and a pin disposedwithin the ring member to be movable along a direction parallel to thecenter axis of the arbor, one end of the pin being in contact with theeccentric cam and the other end of the pin being in contact with an endface of the flange portion or the stopper member.

The eccentric cam is rotated so as to adjust press force that the pinapplies to the end face of the flange portion or the stopper member, tothereby elastically deform a base end portion of the arbor adjacent tothe flange portion in a radial direction in such a manner that tiprun-out of the tool approaches zero.

Preferably, the ring member includes a lock screw for fixing the ringmember to the arbor.

Preferably, the stopper member is removably attached to the arbor bymeans of screw-engagement between the stopper member and the arbor, orby use of a lock screw.

Alternatively, the tip run-out correction mechanism includes a ringmember rotatably fitted onto a base portion of the arbor adjacent to theflange portion; a stopper member provided on the arbor so as to hold thering member at the base portion of the arbor; an operation memberdisposed within the ring member, the operation member extending radiallythrough the ring member and being rotatable about a radially extendingaxis; and a ball element disposed within the ring member to be locatedbetween the operation member and an end face of the flange portion orthe stopper member, the ball element being movable along a directionparallel to the center axis of the arbor.

The operation member is rotated so as to adjust press force that theball element applies to the end face of the flange portion or thestopper member, to thereby elastically deform a base end portion of thearbor adjacent to the flange portion in a radial direction in such amanner that tip run-out of the tool approaches zero.

Preferably, the operation member assumes a cylindrical shape; an arcuatecam groove is formed on an outer circumferential surface of theoperation member so as to be eccentric with respect to the axis of theoperation member; the ball element is received in the cam groove; andthe press force that the ball element applies to the end face of theflange portion or the stopper member is adjusted by means of the camgroove.

Preferably, the ring member includes a lock screw for fixing the ringmember to the arbor.

Preferably, the stopper member is removably attached to the arbor bymeans of screw-engagement between the stopper member and the arbor, orby use of a lock screw.

Preferably, the ring member has a female thread hole for receiving thelock screw; and a thread ridge of the female thread hole is crushed inan area adjacent to the outer circumference of the ring member.

Preferably, the ball element has a flat press surface.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other objects, features and many of the attendant advantages ofthe present invention will be readily appreciated as the same becomesbetter understood by reference to the following detailed description ofthe preferred embodiments when considered in connection with theaccompanying drawings, in which:

FIG. 1 is a partially sectioned side view of a conventional tool holderequipped with a tip run-out correcting mechanism;

FIG. 2 is a partially sectioned side view of another conventional toolholder equipped with a tip run-out correcting mechanism;

FIG. 3 is a longitudinal cross section of a tool holder equipped with atip run-out correcting mechanism according to a first embodiment of thepresent invention;

FIG. 4 is an enlarged cross section of the tool holder of the firstembodiment, taken along line 4-4 in FIG. 3;

FIG. 5 is an enlarged perspective view of an eccentric cam and a run-outcorrection pin used in the tool holder of the first embodiment;

FIG. 6 is a longitudinal cross section of a tool holder equipped with atip run-out correcting mechanism according to a second embodiment of thepresent invention;

FIG. 7 is an enlarged cross section of the tool holder of the secondembodiment, taken along line 7-7 in FIG. 6;

FIG. 8 is a longitudinal cross section of a tool holder equipped with atip run-out correcting mechanism according to a third embodiment of thepresent invention;

FIG. 9 is an enlarged cross section of the tool holder of the thirdembodiment, taken along line 9-9 in FIG. 8;

FIG. 10A is an enlarged view of a cam and a steel ball for run-outcorrection, which are used in the tip run-out correcting mechanism ofthe third embodiment;

FIG. 10B is an enlarged cross section taken along line 10B-10B in FIG.10A; and

FIGS. 11 to 15 are enlarged cross sections of portions of tool holderseach showing a modification of the tip run-out correcting mechanism ofthe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described with reference tothe drawings.

FIG. 3 is a longitudinal cross section of a tool holder equipped with atip run-out correcting mechanism according to a first embodiment of thepresent invention; FIG. 4 is an enlarged cross section of the toolholder of the first embodiment, taken along line 4-4 in FIG. 3; and FIG.5 is an enlarged perspective view of an eccentric cam and a run-outcorrection pin used in the tool holder of the first embodiment.

As shown in FIG. 3, a tool holder 30 for holding a cutting tool 29 suchas a drill or a burnishing reamer has a holder body 31.

The holder body 31 includes a taper shank portion 32 to be attached to amain spindle of an unillustrated machine tool; a flange portion 33,which is formed at a larger-diameter-side end of the shank portion 32; acylindrical support portion 48, which is formed integrally with theflange portion 33 in such a manner that the support portion 48 extendsfrom an end of the flange portion 33 opposite the shank portion 32, andits center axis is aligned with that of the flange portion 33; and acylindrical chuck sleeve 34, which extends from the tip end of thesupport portion 48, and whose center axis is aligned with that of thesupport portion 48. The chuck sleeve 34 has a tapered outercircumferential surface 34 a such that the outer diameter of the chucksleeve 34 gradually decreases from the flange portion 33 toward thedistal end of the chuck sleeve 34.

In FIG. 3, reference numeral 35 denotes a roller retaining sleeve whichis fitted onto the outer circumferential surface of the chuck sleeve 34with a clearance formed therebetween. The roller retaining sleeve 35 isformed of a cylindrical tubular member whose diameter graduallydecreases toward the distal end thereof; i.e., which is tapered at thesame taper angle as that of the tapered outer circumferential surface 34a of the chuck sleeve 34. A stopper ring 36 fitted onto the outerperiphery of a distal end portion of the chuck sleeve 34 holds theroller retaining sleeve 35, while preventing it from coming off thechuck sleeve 34. A large number of needle rollers 37 are received in theroller retaining sleeve 35. The needle rollers 37 are arrangedcircumferentially at fixed intervals in such a manner that the needlerollers 37 are inclined circumferentially at a predetermined angle withrespect to the center axis of the roller retaining sleeve 35. The needlerollers 37 have a diameter greater than the wall thickness of the rollerretaining sleeve 35, whereby portions of the needle rollers 37projecting radially inward from the roller retaining sleeve 35 are incontact with the tapered outer circumferential surface 34 a of the chucksleeve 34, and portions of the needle rollers 37 projecting radiallyoutward from the roller retaining sleeve 35 are in contact with theinner wall surface of a clamp sleeve 38, which will be described below.

The clamp sleeve 38 is adapted to reduce the diameter of the chucksleeve 34 to thereby tightly hold a tool. The clamp sleeve 38 isrotatably fitted onto the outer circumference of the chuck sleeve 34 viathe needle rollers 37, which is held by the roller retaining sleeve 35.The clamp sleeve 38 has a tapered cylindrical inner circumferentialsurface such that the inner diameter of the clamp sleeve 38 graduallydecreases from the flange portion 33 toward the distal end of the clampsleeve 38. Further, a stopper ring 39, serving a seal ring as well, isattached to the inner circumferential surface of the clamp sleeve 38 atan axial position corresponding to a base end portion of the clampsleeve 38 adjacent to the flange portion 33. The stopper ring 39 comesinto contact with the outer circumferential surface of the chuck sleeve34 to thereby provide a seal function, and comes into contact with anend face of the roller retaining sleeve 35 in order to prevent the clampsleeve 38 from coming off the chuck sleeve 34.

In FIGS. 3 and 4, reference numeral 40 denotes a tip run-out correctionmechanism for correcting run-out of the tip of the cutting tool 29. Thetip run-out correction mechanism 40 includes an annular stepped portion41, a ring member 42, an eccentric cam 43, and a pin 44.

The annular stepped portion 41 is formed on the outer circumference ofthe cylindrical support portion 48 to be located at an end of thesupport portion 48, which end faces a rear end face 38 a of the clampsleeve 38, in such a manner that the stepped portion 41 is coaxial withthe support portion 48, and has a diameter smaller than that of the rearend face 38 a of the clamp sleeve 38. Further, an annular groove 48 b isformed in an end face 48 a of the cylindrical support portion 48, fromwhich the chuck sleeve 34 extends axially. The annular groove 48 bincreases the effective length of the chuck sleeve 34 in order tofacilitate radial elastic deformation of the chuck sleeve 34 and radialbending deformation of the chuck sleeve 34 about the base end portion341 of the chuck sleeve 34, which is continuous with the cylindricalsupport portion 48 and serves as a bending point.

The ring member 42 is fitted onto the outer circumference of the annularstepped portion 41 to be rotatable in the circumferential direction. Thering member 42 has a thickness corresponding to the difference betweenthe outer diameter of the flange portion 33 and that of the annularstepped portion 41, and a rectangular cross section. As shown in FIGS. 3and 4, a cam receiving hole 421 and a pin hole 422 communicating withthe cam receiving hole 421 are formed in the ring member 42. The camreceiving hole 421 extends radially through the ring member 42. The pinhole 422 extends from the cam receiving hole 42, through the ring member42, toward the rear end face 38 a of the clamp sleeve 38 along adirection parallel to the center axis of the flange portion 33. Theeccentric cam 43 is fitted into the cam receiving hole 421 to berotatable about a radial direction of the ring member 42. The pin 44 ismovably fitted into the pin hole 422.

As shown in FIGS. 3 and 5, the eccentric cam 43 includes a pair ofsupport flanges 431 rotatably supported by means of the wall surface ofthe cam receiving hole 421; a cam portion 432 extending between thesupport flanges 431 and being eccentric with respect to the center axisof the support flanges 431; and a tool engagement hole 433 formed in onesupport flange 431 exposed at the outer circumference of the ring member42.

One end of the pin 44, which is movably fitted into the pin hole 422, isin contact with the cam portion 432 of the eccentric cam 43, and theother end of the pin 44 is in contact with the rear end face 38 a of theclamp sleeve 38.

As shown in FIG. 4, a balance member 45 is embedded in the ring member42 at a position diametrically opposite the eccentric cam 43 in order toprevent unbalanced rotation of the ring member 42, which would otherwiseresult from provision of the eccentric cam 43.

Further, as shown in FIG. 4, a plurality-of lock screws 46 are providedin the ring member 42 in order to fix the ring member 42 to the annularstepped portion 41 at a desired circumferential position or angularposition. The lock screws 46 extend radially through the ring member 42and are in screw engagement therewith. Further, an annular groove 423 isformed on the outer circumferential surface of the annular steppedportion 41, and the tip ends of the lock screws 46 enter and come intoengagement with the groove 423.

Next, there will be described operation of correcting tip run-out of thecutting tool 29 held by the tool holder 30 by use of the tip run-outcorrection mechanism 40 having the above-described configuration.

First, an operator inserts a shank portion 29 a of the cutting tool 29into the chuck sleeve 34; and subsequently, the operator reduces thechuck sleeve 34 in diameter by use of the clamp sleeve 38 to therebychuck the shank portion 29 aof the cutting tool 29. Next, the operatorattaches the tool holder 30, which carries the cutting tool 29, to amain spindle of an unillustrated machine tool. Subsequently, as shown inFIG. 3, the operator brings a test indicator 28 into contact with acircumferential surface of a tip portion of a cutting portion 29 b ofthe cutting tool 29. The operator measures the difference between themaximum and minimum readings of the test indicator 28 during rotation ofthe main spindle, as tip run-out of the cutting tool 29. Further, fromthe measured value, the operator determines an angular position at whichthe tip run-out of the cutting tool 29 becomes greatest.

Subsequently, after rotation of the main spindle is stopped, theoperator corrects the run-out on the basis of the determined angularposition. Here, it is assumed that at the angular position P1 shown inFIG. 4, as indicated by an imaginary line, the tip of the cuttingportion 29 a deviates to the greatest extent in the direction of arrowA1, whereby the tip of the cutting portion 29 a is located at a shiftedposition indicated by an imaginary line in FIG. 3. In this case, thering member 42 is first rotated to a circumferential position at whichthe eccentric cam 43 coincides with the angular position P1.Subsequently, the operator locks the ring member 42 to the annularstepped portion 41 by use of the lock screws 46. In this state, theoperates engages an unillustrated tool such as a bar spanner with thetool engagement hole 433 of the support flange 431 of the eccentric cam43, and rotates the eccentric cam 43. When the eccentric cam 43 isrotated, the pin 44 moves toward the rear end face 38 a of the clampsleeve 38 by an amount corresponding to the amount of rotation of theeccentric cam 43, and then strongly pushes the rear end face 38 a. As aresult, the chuck sleeve 34 is elastically deformed, in a radialdirection indicated by arrow A2 in FIG. 3, about the base end portion341 of the chuck sleeve 34, which is continuous with the cylindricalsupport portion 48 and serves as a bending point. Specifically, whileviewing the test indicator 28, the operator rotates the eccentric cam 43in the direction for increasing the eccentricity thereof, in order tocorrect the position of the tip of the cutting tool 29 in such a mannerthat the tip of the cutting tool 29, which was located at a deviatedposition indicated by the imaginary line in FIG. 3, moves to a positionindicated by a solid line. In this manner, the tip run-out d (μm) of thecutting tool 29 can be reduced to zero.

In the above-described first embodiment, the base end portion 341 of thechuck sleeve 34, which is continuous with the cylindrical supportportion 48, is elastically deformed in a radial direction in order toreduce the tip run-out of the cutting tool 29 to zero, through anoperation of rotating the eccentric cam 43 provided in the ring member42, which is fitted onto the cylindrical support portion 48 of theholder body 31, to thereby adjust the pressing force which the pin 44applies to the rear end face 38 a of the clamp sleeve 38. Therefore, thetip run-out of the cutting tool 29 can be corrected with small force,and high run-out accuracy can be maintained stably. In addition, therun-out correction mechanism can easily be applied to tool holders forcutting tools of large diameter.

Next, a second embodiment of the present invention will be describedwith reference to FIGS. 6 and 7.

FIG. 6 is a longitudinal cross section of a tool holder equipped with atip run-out correcting mechanism according to the second embodiment ofthe present invention; and FIG. 7 is an enlarged cross section of thetool holder of the second embodiment, taken along line 7-7 in FIG. 6.

As shown in FIG. 6, a tool holder 50 for holding a cutting tool 29 suchas a drill or a burnishing reamer has a holder body 51. The holder body51 includes a taper shank portion 52 to be attached to a main spindle ofan unillustrated machine tool; a flange portion 53, which is formed atan end of the shank portion 52 and whose center axis is aligned withthat of the shank portion 52; an arbor 54, which is formed integrallywith the flange portion 53 in such a manner that the arbor 54 extendsfrom an end of the flange portion 53 opposite the shank portion 52, andits center axis is aligned with that of the flange portion 53; and achuck 55 for holding the cutting tool 29 at the tip end of the arbor 54.

A tip run-out correction mechanism 60 for correcting run-out of the tipof the cutting tool 29 is removably attached to a root portion of thearbor 54.

As shown in FIGS. 6 and 7, the tip run-out correction mechanism 60includes a ring member 61, a stopper member 62, an eccentric cam 63, anda pin 64. The ring member 61 is rotatably fitted onto a base portion 54a of the arbor 54 adjacent to the flange portion 53. The stopper member62 is removably screw-engaged with a male thread portion 54 b formed onthe arbor 54, in order to hold the ring member 61 on the root portion 54a.

As shown in FIGS. 6 and 7, a cam receiving hole 611 and a pin hole 612communicating with the cam receiving hole 611 are formed in the ringmember 61. The cam receiving hole 611 extends radially through the ringmember 61. The pin hole 612 extends from the cam receiving hole 611,through the ring member 61, toward the front end face 53 a of the flangeportion 53 along a direction parallel to the center axis of the flangeportion 53. The eccentric cam 63 is fitted into the cam receiving hole611 to be rotatable about a radial direction of the ring member 61. Thepin 64 is movably fitted into the pin hole 612.

As shown in FIGS. 6 and 7, the eccentric cam 63 includes a pair ofsupport flanges 631 rotatably supported by the wall surface of the camreceiving hole 611; a cam portion 632 extending between the supportflanges 631 and being eccentric with respect to the center axis of thesupport flanges 631; and a tool engagement hole 633 formed in onesupport flange 631 exposed at the outer circumference of the ring member61.

One end of the pin 64, which is movably fitted into the pin hole 612, isin contact with the cam portion 632 of the eccentric cam 63, and theother end of the pin 64 is in contact with the front end face 53 a ofthe flange portion 53.

As shown in FIG. 7, a plurality of lock screws 65 are provided in thering member 61 in order to fix the ring member 61 to the arbor 54 at adesired circumferential position or angular position. The lock screws 65extend radially through the ring member 61 and are in screw engagementtherewith.

Next, there will be described operation of correcting tip run-out of thecutting tool 29 held by the tool holder 50 by use of the tip run-outcorrection mechanism 60 having the above-described configuration.

First, an operator attaches the cutting tool 29 to the tip end of thearbor 54 of the holder body 51 by means of the chuck 55, and thenattaches the tool holder 50, which carries the cutting tool 29, to amain spindle of an unillustrated machine tool. Subsequently, as shown inFIG. 6, the operator brings a test indicator 28 into contact with acircumferential surface of a tip portion of a cutting portion 29 b ofthe cutting tool 29. The operator measures the difference between themaximum and minimum readings of the test indicator 28 during rotation ofthe main spindle, as tip run-out of the cutting tool 29. Further, fromthe measured value, the operator determines an angular position at whichthe tip run-out of the cutting tool 29 becomes greatest.

Subsequently, after rotation of the main spindle is stopped, theoperator corrects the run-out on the basis of the determined angularposition. Here, it is assumed that at the angular position P1 shown inFIG. 7, as indicated by an imaginary line, the tip of the cuttingportion 29 a deviates to the greatest extent in the direction of arrowA1, whereby the tip of the cutting portion 29 a is located at a shiftedposition indicated by an imaginary line in FIG. 6. In this case, thering member 61 is first rotated to a circumferential position at whichthe eccentric cam 63 coincides with the angular position P1.Subsequently, the operator locks the ring member 61 to the arbor 54 byuse of the lock screws 65. In this state, the operates engages anunillustrated tool such as a bar spanner with the tool engagement hole633 of the support flange 631 of the eccentric cam 63, and rotates theeccentric cam 63. When the eccentric cam 63 is rotated, the pin 64 movestoward the front end face 53 a of the flange portion 53 by an amountcorresponding to the amount of rotation of the eccentric cam 63, andstrongly pushes the front end face 53 a. As a result, the arbor 54 iselastically deformed, in a radial direction indicated by arrow A2 inFIG. 6, about the base end portion 54 a of the arbor 54, which iscontinuous with the flange portion 53 and serves as a bending point.Specifically, while viewing the test indicator 28, the operator rotatesthe eccentric cam 63 in the direction for increasing the eccentricitythereof, in order to correct the position of the tip of the cutting tool29 in such a manner that the tip of the cutting tool 29, which waslocated at a deviated position indicated by the imaginary line in FIG.6, moves to a position indicated by a solid line. In this manner, thetip run-out d (μm) of the cutting tool 29 can be reduced to zero.

In the above-described second embodiment, the base end portion 54 a ofthe arbor 54, which is continuous with the flange portion 53, iselastically deformed in a radial direction in order to reduce the tiprun-out of the cutting tool 29 to zero, through an operation of rotatingthe eccentric cam 63 provided in the ring member 61 to thereby adjustthe pressing force which the pin 64 applies to the front end face 53 aof the flange portion 53. Therefore, the tip run-out of the cutting tool29 can be corrected with small force, and high run-out accuracy can bemaintained stably. In addition, the run-out correction mechanism can beeasily applied to tool holders for cutting tools of large diameter.

In addition, in the second embodiment, the ring member 61, whichincludes the eccentric cam 63 and the pin 64 and which constitutes thetip run-out correction mechanism 60, is held by means of the stoppermember 62, which is removably attached to the arbor 54. Therefore, thetip run-out correction mechanism 60 can be easily applied to existingtool holders. In addition, a user is required to purchase only the tiprun-out correction mechanism 60, which is economical.

Next, a third embodiment of the present invention will be described.

FIG. 8 is a longitudinal cross section of a tool holder equipped with atip run-out correcting mechanism according to the third embodiment ofthe present invention; FIG. 9 is an enlarged cross section of the toolholder of the third embodiment, taken along line 9-9 in FIG. 8; FIG. 10Ais an enlarged view of a cam and a steel ball for run-out correction,which are used in the tip run-out correcting mechanism of the thirdembodiment; and FIG. 10B is an enlarged cross section taken along line10B-10B in FIG. 10A.

In FIGS. 8 and 9, structural elements identical with those shown inFIGS. 3 and 4 are denoted by the same reference numerals, and theirrepeated descriptions are omitted. Portions different from those of inFIGS. 3 and 4 will mainly be described.

The tool holder shown in FIGS. 8 and 9 differs from the tool holdershown in FIGS. 3 and 4 in that the tool holder shown in FIGS. 8 and 9has a different tip run-out correction mechanism 80 for correcting tiprun-out of the cutting tool 29. The tip run-out correction mechanism 80includes an annular stepped portion 81, a ring member 82, an operationmember 83, and a steel ball 84.

The annular stepped portion 81 is formed on the outer circumference ofthe cylindrical support portion 48 to be located at an end of thesupport portion 48, which end faces a rear end face 38 a of the clampsleeve 38, in such a manner that the stepped portion 81 is coaxial withthe support portion 48, and has a diameter smaller than that of the rearend face 38 a of the clamp sleeve 38.

The ring member 82 is fitted onto the outer circumference of the annularstepped portion 81 to be rotatable in the circumferential direction. Thering member 82 has a thickness corresponding to the difference betweenthe outer diameter of the flange portion 33 and that of the annularstepped portion 81, and a rectangular cross section. As shown in FIGS. 8and 9, a cylindrical receiving hole 821 and a guide hole 822communicating with the receiving hole 821 are formed in the ring member82. The receiving hole 821 radially extends through the ring member 82.The guide hole 822 extends from the receiving hole 821, through the ringmember 82, toward the rear end face 38 a of the clamp sleeve 38 along adirection parallel to the center axis of the flange portion 33. Theoperation member 83 is fitted into the receiving hole 821 to berotatable about a radial direction of the ring member 82. The steel ball84 is movably fitted into the guide hole 822.

As shown in FIGS. 8, 10A and 10B, the operation member 83 has acylindrical columnar shape having a diameter corresponding to that ofthe receiving hole 821. An arcuate cam groove 831 is formed over theentire circumference of the operation member 83 in such a manner thatthe cam groove 831 is eccentric with respect to the axis of theoperation member 83. The steel ball 84 engages the cam groove 831. Thecam grove 831 has an arcuate bottom surface having a radius of curvaturecorresponding to the diameter of the steel ball 84. A tool engagementhole 832 is formed in an end surface of the operation member 83, whichend surface is exposed at the outer circumference of the ring member 82.

As shown in FIG. 9, a balance member 85 is embedded in the ring member82 at a position diametrically opposite the operation member 83 in orderto prevent unbalanced rotation of the ring member 82, which wouldotherwise result from provision of the operation member 83.

Further, as shown in FIG. 9, a plurality of lock screws 86 are providedin the ring member 82 in order to fix the ring member 82 to the steppedportion 81 at a desired circumferential position or angular position.The lock screws 86 radially extend through the ring member 82 and are inscrew engagement therewith. Further, an annular groove 411 is formed onthe outer circumferential surface of the annular stepped portion 81, andthe tip ends of the lock screws 86 enter and come into engagement withthe groove 411.

Further, a thread ridge 824A of each female thread hole 824 forreceiving the lock screw 86 is crushed in an area adjacent to the outercircumference of the ring member 82, in order to prevent the lock screws86 from coming off the female thread hole 824 of the ring member 82.Reference numeral 861 denotes an elastic member formed of rubber whichis disposed between the tip of each of the lock screws 86 and thecylindrical support portion 48. Notably, the lock screws 86 are screwedinto the female thread hole 824 from inside the ring member 82.

Next, there will be described operation of correcting tip run-out of thecutting tool 29 held by the tool holder 30 by use of the tip run-outcorrection mechanism 80 having the above-described configuration.

First, an operator inserts a shank portion 29 a of the cutting tool 29into the chuck sleeve 34; and subsequently, the operator reduces thechuck sleeve 34 in diameter by use of the clamp sleeve 38 to therebychuck the shank portion 29 aof the cutting tool 29. Next, the operatorattaches the tool holder 30, which carries the cutting tool 29, to amain spindle of an unillustrated machine tool. Subsequently, as shown inFIG. 8, the operator brings a test indicator 28 into contact with acircumferential surface of a tip portion of a cutting portion 29 b ofthe cutting tool 29. The operator measures the difference between themaximum and minimum readings of the test indicator 28 during rotation ofthe main spindle, as tip run-out of the cutting tool 29. Further, fromthe measured value, the operator determines an angular position at whichthe tip run-out of the cutting tool 29 becomes greatest.

Subsequently, after rotation of the main spindle is stopped, theoperator corrects the run-out on the basis of the determined angularposition. Here, it is assumed that at the angular position P1 shown inFIG. 9, as indicated by an imaginary line, the tip of the cuttingportion 29 a deviates to the greatest extent in the direction of arrowA1, whereby the tip of the cutting portion 29 a is located at a shiftedposition indicated by an imaginary line in FIG. 8. In this case, thering member 82 is first rotated to a circumferential position at whichthe operation member 83 coincides with the angular position P1.Subsequently, the operator locks the ring member 82 to the annularstepped portion 81 by use of the lock screws 86. In this state, theoperates engages an unillustrated tool such as a bar spanner with thetool engagement hole 832 of the operation member 83, and rotates theoperation member 83. When the operation member 83 is rotated, the ball84 moves toward the rear end face 38 a of the clamp sleeve 38 by anamount corresponding to the amount of rotation of the operation member83 through the action of the cam groove 831 of the operation member 83,and then strongly pushes the rear end face 38 a. As a result, the chucksleeve 34 is elastically deformed, in a radial direction indicated byarrow A2 in FIG. 8, about the base end portion 341 of the chuck sleeve34, which is continuous with the cylindrical support portion 48 andserves as a bending point. Specifically, while viewing the testindicator 28, the operator rotates the operation member 83 in order tocorrect the position of the tip of the cutting tool 29 in such a mannerthat the tip of the cutting tool 29, which was located at a deviatedposition indicated by the imaginary line in FIG. 8, moves to a positionindicated by a solid line. In this manner, the tip run-out d (μm) of thecutting tool 29 can be reduced to zero.

In the above-described third embodiment, the base end portion 341 of thechuck sleeve 34, which is continuous with the cylindrical supportportion 48, is elastically deformed in a radial direction in order toreduce the tip run-out of the cutting tool 29 to zero, through anoperation of rotating the operation member 83 provided in the ringmember 82, which is fitted onto the cylindrical support portion 48 ofthe holder body 31, to thereby adjust the pressing force which the steelball 84 applies to the rear end face 38 a of the clamp sleeve 38.Therefore, the tip run-out of the cutting tool 29 can be corrected withsmall force, and high run-out accuracy can be maintained stably. Inaddition, the tip run-out correction mechanism can be easily applied totool holders for cutting tools of large diameter.

Next, a modification of the tip run-out correction mechanism 80 will bedescribed with reference to FIG. 11.

FIG. 11 is an enlarged cross section of a portion of the tip run-outcorrecting mechanism according to the present modification. In the tiprun-out correction mechanism 80 shown in FIG. 11, the steel ball 84 ispartially cut in order to form a flat press surface 841, which isbrought into contact with the rear end face 38 a of the clamp sleeve 38.This configuration reduces the surface pressure produced between thesteel ball 84 and the rear end face 38 a of the clamp sleeve 38, andmitigates damage to their contact surfaces.

Next, a modification in which the tip run-out correction mechanism 80 ofFIG. 8 is applied to the tool holder 60 of FIG. 6 will be described withreference to FIG. 12, which is an enlarged cross section of a portion ofthe tip run-out correcting mechanism according to the presentmodification.

In the modification shown in FIG. 12, the operation member 83 of the tiprun-out correction mechanism 80 is fitted into the cam receiving hole611 of the ring member 61; a guide hole 613 extending from the camreceiving hole 611 to the end face 53 a of the flange portion 53 isformed along a direction parallel to the center axis of the arbor 54;and the steel ball 84 is movably fitted into the guide hole 613.

In the tip run-out correction mechanism 80 modified in theabove-described manner, as in the case of the tip run-out correctionmechanism shown in FIG. 6, an operator can correct tip run-out of acutting tool through an operation of adjusting the press force that thesteel ball 84 applies to the back end face 38 a of the clamp sleeve 38,by means of rotating the operation member 83.

The tool holder according to the modified embodiment shown in FIG. 12,which uses a steel ball instead of a pin, provides the same action andeffects as those attained in the case of the tool holder shown in FIG.6.

Notably, in the modification shown in FIG. 12, a portion of the steelball 84 to come into pressure-contact with the end face 53 a of theflange portion 53 may be cut to provide a flat press surface as in thecase shown in FIG. 11.

Next, a modification of the tip run-out correction mechanism applied toa tool holder having a structure shown in FIG. 3 will be described withreference to FIG. 13, which is an enlarged cross section of a portion ofthe tip run-out correcting mechanism according to the presentmodification.

As in the case shown in FIG. 3, in the tip run-out correction mechanism40 shown in FIG. 13, the eccentric cam 43 is rotatably fitted into thecam receiving hole 421 of the ring member 42. Further, a pin hole 423extending from the cam receiving hole 421 to the end face 411 of theannular stepped portion 41 is formed along a direction parallel to thecenter axis of the flange portion 33; and the pin 44 is movably fittedinto the pin hole 423.

In the tip run-out correction mechanism 40 modified in theabove-described manner, as in the case of the tip run-out correctionmechanism shown in FIG. 3, an operator can correct tip run-out of acutting tool through an operation of adjusting the press force that thepin 44 applies to the end face 411 of the annular stepped portion 41, bymeans of rotating the eccentric cam 43.

Next, a modification of the tip run-out correction mechanism applied toa tool holder having a structure shown in FIG. 8 will be described withreference to FIG. 14, which is an enlarged cross section of a portion ofthe tip run-out correcting mechanism according to the presentmodification.

In the modification shown in FIG. 14, as in the case shown in FIG. 8,the operation member 83 of the tip run-out correction mechanism 80 isfitted into the receiving hole 821 of the ring member 82; a guide hole822 extending from the receiving hole 821 to the end face 411 of theannular stepped portion 81 is formed along a direction parallel to thecenter axis of the support portion 48; and the steel ball 84 is movablyfitted into the guide hole 822.

In the tip run-out correction mechanism 80 modified in theabove-described manner, as in the case of the tip run-out correctionmechanism shown in FIG. 8, an operator can correct tip run-out of acutting tool through an operation of adjusting the press force that thesteel ball 84 applies to the end face 411 of the annular stepped portion81, by means of rotating the operation member 83.

Next, a modification of the tip run-out correction mechanism applied toa tool holder having a structure shown in FIG. 6 will be described withreference to FIG. 15, which is an enlarged cross section of a portion ofthe tip run-out correcting mechanism according to the presentmodification.

As in the case shown in FIG. 6, in the tip run-out correction mechanism40 shown in FIG. 15, the eccentric cam 43 is rotatably fitted into thecam receiving hole 421 of the ring member 42. Further, a pin hole 424extending from the cam receiving hole 421 to the stopper member 62 isformed along a direction parallel to the center axis of the arbor 54;the pin 44 is movably fitted into the pin hole 424.

In the tip run-out correction mechanism 40 modified in theabove-described manner, as in the case of the tip run-out correctionmechanism shown in FIG. 8, an operator can correct tip run-out of acutting tool through an operation of adjusting the press force that thepin 44 applies to the stopper member 62, by means of rotating theeccentric cam 43.

Notably, in the second embodiment, the stopper member 62 is fixed to thearbor 54 by means of screw engagement. However, the present invention isnot limited thereto, and the stopper member 62 may be fixed to the arbor54 by use of a lock screw which radially penetrates the ring member 61and is in screw-engagement with the ring member 61.

In the first embodiment, the shank portion 29 a of the cutting tool 29is inserted directly into the chuck sleeve 34 and is then chucked.However, the present invention is not limited thereto, and the shankportion 29 a of the cutting tool 29 may be held via a collet.

Although the first embodiment uses a roller-lock type chuck configuredin such a manner that the clamp sleeve 38 is fitted onto the chucksleeve 34 via the needle rollers 37, the present invention is notlimited thereto; the present invention can be applied to tool holderswhich employ other types of chucks, such as a ball-screw-type chuckconfigured in such a manner that a groove having a semicircular crosssection is spirally formed on each of the outer circumferential surfaceof the chuck sleeve 34 and the inner circumferential surface of theclamp sleeve 38, and a large number of steel balls are disposed in thespiral grooves.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, thepresent invention may be practiced otherwise than as specificallydescribed herein.

1. A tool holder comprising: a holder body having an elasticallydeformable tool attaching portion adapted to receive a tool; a ringmember rotatable about a center axis of the holder body but not movablealong the center axis; a cylindrical member adapted to be locatedadjacent to the ring member; and a force generation mechanism providedin the ring member and adapted to generate a force in a directionsubstantially parallel to the center axis to actuate the cylindricalmember so that the tool attachment portion is elastically deformed in aradial direction perpendicular to the center axis such that tip run-outof the tool approaches zero; wherein the force generation mechanismcomprises: an operation member disposed within the ring member, theoperation member extending radially through the ring member and beingrotatable about a radially extending axis; and a ball element disposedwithin the ring member and located between the operation member and theholder body or the cylindrical member; wherein the operation member isrotated so as to adjust the force that the ball element applies to theholder body or the cylindrical member, to thereby elastically deform thetool attaching portion in such a manner that tip run-out of the toolapproaches zero.
 2. The tool holder according to claim 1 wherein theoperation member assumes a cylindrical shape; an arcuate cam groove isformed on an outer circumferential surface of the operation member so asto be eccentric with respect to the axis of the operation member; theball element is received in the cam groove; and the force that the ballelement applies to the holder body or the cylindrical member is adjustedby means of the cam groove.
 3. The tool holder according to claim 1,wherein the ball element has a flat press surface.
 4. The tool holderaccording claim 1, wherein the ball element comprises a steel ball.